Surface measuring apparatuses of this type are generally known, for example in the form of roughness measurement apparatuses. They have a probe that includes a probe arm bearing a probe element for contacting a surface of a workpiece to be measured. The known surface measuring apparatuses also have a feed apparatus for moving the probe element relative to the workpiece to be measured. The probe arm is exchangeable to allow the surface measuring apparatus to be adapted to different measuring tasks. For this purpose, the probe arm is detachably connectable or connected to a movable part of the feed apparatus via a mechanical interface, the interface having a first part and a second part which in the installed position of the probe arm are connected to one another with static determinacy on the movable part of the feed apparatus, one part being associated with the probe arm and the other part being associated with the feed apparatus.
The surface measuring apparatus may thus be adapted to different measuring tasks by the selection and use of an appropriate probe arm.
When the probe arm is exchanged, it must be mounted in a predetermined, defined position on the movable part of the feed apparatus. Otherwise, the actual geometry of the probe would depart, in an undefined manner, from a predetermined geometry on which the evaluation of the probe output signals is based. However, reliable reconstruction of the surface of the workpiece to be measured, based on the probe output signals, is possible only when the geometry of the probe is precisely known.
There is a risk in particular that a slight deviation of the actual position of the probe arm from the predetermined position may result in impairment of the measuring accuracy without this error being noticed. The risk of an incorrect installation of the probe arm is further increased due to the fact that the probe arm is frequently held on the movable part of the feed apparatus by magnetic force, and in principle, installation of the probe arm in various positions on the movable part of the feed apparatus is thus possible.
To simplify installation of the probe arm in the intended correct position, it is known to use alignment aids in the form of visual markings. However, it is disadvantageous that the interface is often not visible. In addition, in particular for small components, a slight misalignment is often not recognizable.